86 Botanical Re^niniscences. 
covering tlie tops of tlie trees, and forming, in their abundance, 
islands of yellow flowers in the changing sea of vegetatiou. 
The luxuriant and rapid development of the vegetation of 
the trees and shrubs is assisted by the moist atmosphere of 
the* forest in the growth of the wonderful Orchids , the Avoids^ 
Piperaceae, and Bromeliaceae, which cover the branches and 
trunks of the trees, and display in manifold gradation their 
peculiar formation of flowers. 
The Sandstone Region. 
The first elevations of the sandstone formation from the 
coast we find on the banks of the rivers Mazaruni and Cuyuni, 
both tributaries of the Essequibo. At the Cuyuni the sand- 
stone appears under 6° 2' north latitude. The ground 
suddenly rises several thousand feet in wall-like clifis, and 
forms for the next hundred miles a table-land. In this re- 
markable group of mountains we find the Roraima, at its 
easterly point of culmination, up to an absolute height of 
8,000 feet above the level of the sea. As suddenly as the 
sandstone region begins it again ceases under the ^ 30' 
north latitude, in the Ilumirida Mountains, where quartz 
and granite appear. 
The valleys of the large plateau, generally of a height 
of 3,000 feet above the sea, are savannas — they interchange 
with steep mountainous clifis, small cavities, large high table- 
lands, and hills of 4,000 to 8,000 feet. 
The region of the sandstone possesses an extraordinary 
abundance of springs, and it is intersected by numerous 
rivers and rivulets, which, almost without exception, have their 
origin in the summits of the mountains. 
The quantity of rain which falls in this region, during 
the whole year, even exceeds the quantity which falls 
along the coast, as it may be always fixed at 100 inches, 
while the medium temperature does not exceed 73'' Fahr. 
The sandstone appears in three principal modifications ; 
first, fine-grained reddish, and - containing small scales of 
white mica ; secondly, as a variegated sandstone ; and, thirdly, 
a flinty, solid sandstone. In some places appears jasper in 
great masses. As far as abundance and change of vegetation 
are concerned, no other country could be compared with this 
region. A change in the soil, difference of altitude, or change 
in the stratum (may they ever be so insignificant relative to 
their neighborhood), a deviation in the degree of humidity — 
